Mill-drying process and apparatus



13w 1935. w. B. S ENSEMAN 2,023,247

MILL DRYING PROCESS AND APPARATUS Filed Dec. 29, 1952 2 Sheets-Sheet 1 Dec. 3,- 1935. w. B. SENSEMAN 2,023,247

MILL DRYING PROCESS AND APPARATUS Filed Dec. 29, 1932 2 Sheets-Sheet 2 Irufenif); 2/27/2220? fldenseman orllgys.

Patented Dec. 3, 1935 UNITED. STATES PATENT OFFICE MILL-DRYING PROCESS AND APPARATUS William B. Senseman, Glendale, Calii., assignor to The Raymond Brothers Impact Pulverizer Company, Chicago, 111., a corporation of Illinois Application December 29, 1932, Serial No. 649,307

5 Claims. (Cl. 83-11 material together with highly heated gases is fed into a mill, preferably of theimpact pulverizer type. The material is violently agitated andbeaten while within the mill in the presence of the hot gases and reduced to a finely divided or pulverized condition. A large percentage of the moisture is vaporized and carried away from the mill together with the gases, and the material to be dried remains in the mill until it has been so finely divided that it can be carried away in suspension in the gas stream by which time its moisture content has been reduced to the desired extent. The gas stream with the suspended maeterial is passed into a cyclone separator wherein the dried solid material is separated out. According to the present invention, this mill drying process is applied to the drying and reducing of raw material having a very high moisture content. The raw material may be in the form of a heavy liquid, or semi-liquid or liquid and solid mixture, for example, blood from a slaughter house, or fruit pulp, such as oranges from which the juice has been pressed. Material of this type is often of such a wet and sticky nature that it is difficult to handle and introduce into the mill, and its sticky or gummy nature is such that it will interfere with the successful operation of the feeding and pulverizing mechanism. According to the present invention, a portion of the dried and pulverized material removed from the separator is fed into a mixer together with the raw wet material in such proportions as to form a mixture 'capable'of being easily and economically handled in the feeding and pulverizing apparatus.

The principal object of this invention is to provide an improved mill-drying process and apparatus such as briefly described hereinabove and disclosed more in detail in the specifications which follow.

Another. object is to provide an improved process and apparatus for removing water from a raw material having a high moisture content. v

Another object is to provide an improved milldrying process in which dried and pulverized material is re-circulated through the mill.

Another object is to provide an improved closed circulation mill-drying process in which a portion of the dried material and a portion of the.

- 9, pivotally mounted on the shaft hot gases are separately removed from the circulating system, a portion of the material and a portion of the hot gases are re-circulated through the system, and raw wet material and fresh hot gases are added to the circulating system in prop- 5 er proportion to replace the dried material and gases that are removed therefrom.

Other objects and advantages of this invention will be more apparent from the following detailed description of one approved form of appal0 1 ratus constructed and operating according to the principles of this invention.

In the accompanying drawings:

Fig. 1 is a diagrammatic elevation showing a group of apparatus and devices suitably connected and combined for carrying out this process.

Fig. 2 is a longitudinal vertical section through a pulverizing mill of the type preferably used in this process. I

The apparatus preferably comprises a mill A in which the material is ground and the moisture removed, a separator B in which the ground and dried material is separated from the gas stream,

a surge bin C for returning a portion of the dried material to the circulation system, a mixer D for combining the raw wet material with the dried material which is returned, a concentrator E for venting a portion of the moisture-laden gas stream and returning the concentrated finely divided material in suspension in the remainso der of this gas stream to the circulation system,

a source of heated air or other gases indicated at F, and a device G for feeding the hot gases and mixed materials back into the mill A.

Referring now more particularly to Fig. 2, the mill here shown by way of example, which is the type preferred for use in this system, is substantially of the type disclosed in the. patent to Crites 1,573,040 granted February 16, 1926. The mill comprises a feeding compartment l, a beater chamber 2, and a fan chamber 3. The shaft Q which carries the principal rotating elements of the mill extends through these chambers and is mounted adjacent its ends, outside of the mill, in bearings 5 and 6, there being a connection '7 at one end of the shaft through which it is rotated by any suitable driving means, such as the motor 8 (seeF'ig. l) The beater element of the mill comprises a plurality of swing hammers 4 by means of 59 collars l0 and pivot pins H. The pulverizing chamber 2 is provided with suitable liners l2, and

when the mill is in operation the hammers 9 are normally held in radial position by centrifugal force with their heads adjacent the liners i2.

the rate of flow of material therethroughyab The material is pulverized by impact with the hammers 9, and in cooperation'with the liners I2, I

the material being thrown by centrifugal force outwardly aganst the liner members.

About the periphery of the tapering passage i3 which connects the pulverizing chamber 2 with the'fan chamber 3 is positioned the conical ring l4. The regulator l5 comprises a series of radially disposed plates IS, the regulator being secured to shaft 4 and adjustable longitudinally of the shaft. The plates l6 are also adjustable radially so as to vary the distance between the ends ofthe plates and the face of the ring I4.

A fan I1 is mounted on shaft 4 within the fan chamber 3, and when this fanv is rotated in the proper operating direction, air and material carried in suspension therein will be drawn from beater chamber 2 throughpassage, i3-and forced out of the fan chamber 3 through the outlet passage 18. The regulator l5 serves to impede dried or de-hydrated are introduced by gravity into the feeding chamber or hopper l and are deflected by the inclined lower wall thereof into the beater chamber 2. If desired, a feeding device may be positioned in hopper I to graduate though this feeding is not ordinarily required.

The hot gases are also introduced into the mill through this chamber I. The initial temperature of these gases will -vary with the character of the material to be operated uponand the size of the mill, but the temperature of the gases should ordinarily be sufliclent to quickly vaporize any exposed moisture, and to prevent this moisture from condensing until the pulverized material has been withdrawn from the gas stream.

The mill A, as hereinabove briefly described, need not differ in any essential features from mills of this type heretofore usedexclusively for pulverizing or grinding purposes, except that it is preferably designed to withstand the comparatively high temperaturesto which it is subjected, and the bearings 5 and 6 may be water-cooled for this purpose. The length of time that the materials will remain within the mill depends, in

part on the length of the mill and the number of series of beaterv units 9 therein. In the particular process herein disclosed, in which the materials to be de-hydrated have a very large percentage of moisture, the mill will preferably be longer and comprise a greater number of heaters 9 than is usual in the ordinary pulverizing mill. The size and proportions of the mill and the number of heaters 9 used will vary with the size and capacity of the installation and the character of the material to be de-hydrated.

The hot gases will lose a portion of their heat and suffer a loss in temperature while within the mill A, but will still be at a sufllciently high temperature after being discharged from the fan chamber 3 to maintain all of the separated moisture in suspension. The combined steam and hot gases, and the pulverized material carried in suspension thereby, are forced by fan I! through.

outlet l8 and conduit 2| into the upper portion It keeps the gases and solid mat-- of separator B, which may be a cyclone separator of well known type. The de-hydrated and pulverized material flows down through pipe 22 into the surge bin C which may be an ordinary closed receptacle having a conical lower portion 23 for greater portion of the.suspended solid material,

is withdrawn from the upper portion of separator B through pipe 26 by means of fan 21 and is discharged through pipe or conduit 28-into aconcentrator E of suitabletype, in which the remain-1 ing finely divided pulverized material is concentrated and carried downwardly in suspension in a small proportion of the gases through pipe 2!]. The larger portion of the gases are vented through pipe 30 from the upper portion of concentrator E. I

At F is indicated any suitable type of heater for supplying the hot air or other gases, the heater having a stack 3|, and the heated air being drawn ofl through pipe or conduit 32. At 33 is indicated a valved inlet through which cool fresh air may be drawn in to dilute the air stream and reduce it to the desired temperature. This hot air stream may be combined at 34 with the remainden of theoriginalair stream returned through conduit 29, and this replenished air stream is drawn through pipe 35 and is discharged into the upper portion of the vertical conduit-or 40 drying tower G. Alternatively, only the fresh hot gases may be drawn into the upper portion of tower G at 35, andthe pipe 29 may discharge the,

remainder of the original air stream into the lower portion of tower G or directly into hopper I. i

The" raw wet material, which may be in liquid or semi-liquid form, or a solid containing such a high .moisture content that it is sticky and will tend to clog up the apparatus, is introduced into the upper portion of mixer D through the conduit 36 provided with the adjustable feeder 31. Thefeeder 24 is so adjusted that a suitable proportion of dry material from the storage bin C is simu1-' taneously introduced into the mixer D, which comprises a suitably driven screw conveyor 33 which mixes together the-dry and wet materials andpropels them toward the opening 39 through that the mixture can be handled through the.

mixer D, tower G and mill A without unduly clogging the mechanisms.

At 40 is indicated an automatic seal mechanism the purpose of which is to out off, as far as possible, the upward flow of heated gases while permitting the mixed materials from mixer D to be discharged or sprinkled downwardly through the aoaaaar which communicatesat its lower end 42 with the material having a high feeding chamber l of the mill. Some of the surface moisture will be removed from the material during its passage through tower G before it enters the mill.

It will now be seen that this apparatus forms a closed circulation system in which a portion of the solid material, and a portion of the hot gases,

are more or less continuously re-circulated. The I dry material circulates from mill A through conduit 2|, separator B, conduit 22, bin C, mixer D and tower G back into the mill. The gases circulate from mill A through conduit 2 i separator B, fan 21, conduit 28, concentrator E, conduits 29 and 35, and tower G back into the mill. The dry pulverized material produced in excess of that required for re-circulationis discharged through conduit 25 from the upper portion of'binC. A portion of the moisture-laden gases are vented from the circulation system through pipe 313 leading from the top of concentrator E. The circulation system is replenished with raw wet material through conduit 36 leading into mixer D, and with hot gases through conduit 32 leading through the heater F.

It may also be noted that what may be termed a re-circulation of the wet material takes place within the spray drier, the wet material and the heated air are passed through a drying chamber in contact with one another, but there is no provision for retaining the moist material in suspension within the chamber or recirculating it therein until the desired dehydration has been obtained. In the mill used in this installation, the wet material is continuously churned or recirculated within the mill by means of the rotating beaters 9 until it has been reduced to such a finely divided and dehydrated condition that it can be carried out in suspension in the gases through the regulator 85, and by proper adjustment of the apparatus substantially any desired percentage of moisture content can be removed.

The relative proportions of dry and wet material fed into the mixer G will vary with the character and moisture content of the raw wet material to be dehydrated. Usually at least an equal bulk or volume of dry material will be returned and added to the raw wet material, and sometimes the bulk of dry material returned will be ten or twelve times the bulk of the wet material in order to secure the best results. In this manner, raw materials having an initial moisture content in excess of 90% can be successfully dehydrated. The temperature of the hot gases used may be as high as 2000 Fahrenheit at the entrance to the mill, although with some materials lower temperatures are suflicient. The temperature of the gas stream will drop considerably before being discharged from the mill through conduit 2|, but should in all cases remain above the dew-point, that is remain high enough to prevent condensation of the removed moisture.

I claim:

1. An apparatus for removing water from raw moisture content, comprising a pulverizng mill, a separator, a conduit through which dried and pulverized material is carried from the mill into the separator in suspension in heated gases, a surge bin into which the dried material is discharged from the sepaq rator, means for discharging excess dried material irom the upper portion of the bin, a mixer,

mill A itself. In the ordinary type of r I space and back means for feeding raw material into the mixer, means for feeding dried material from the bin into the mixer, a source of heated gases, and means for feeding mixed material from the mixer and heated gases from the source into the mill.

2. An apparatus for removing water from. raw material having a high moisture content,-comprising a pulverizing mill, a separator, a conduit through which dried and pulverized material is carried from the mill into the separator in suspension in heated gases, a surge bin into which the dried material is discharged from the separator, means for discharging excess dried material from the upper portion of the bin, a mixer, means for feeding raw material into the mixer, means from the concentrator concentrated material suspended in a portion of the gases, means for venting the remainder of the gases, means for replenishing the gas stream with fresh. heated gases, and means for feeding materials from-the mixer into this gas stream and thence into the mill.

3. The process of removing water from a raw material having a high moisture content which consists in mixing a measured quantity of previously dried material with a measured quantity of the raw material so as to obtain a mixture of predetermined moisture content, introducing this mixture together with heated gases into an enclosed space, grinding the material in the enclosed space and removing the ground and dried material in suspension in the gases, separating the dried material-from the gases, retaining a suficlent quantity of the dried material to form the mixture, withdrawing the excess dried material, concentrating the flne materials remaining in the gases separated from the dried material in a gas stream which is returned to the grinding space and venting the remainder of these gases, and adding dry heated gases to the returned gas stream.

4. The process of removing water from a raw material having a high'moisture content which consists in continuously mixing a measured flow of previously dried material with a measured flow of the raw material so as to obtain a mixture of predetermined moisture content, introducing this mixture together with heated gases into an enclosed space, grinding the material in the enclosed space and removing the ground and dried material in suspension in the gases, separating concentrating the line materials remaining in the gases separated from the dried material in a gas stream which is returned to the grinding space and venting the remainder of these gases, and adding dry heated gases to the returned gas stream.

5. The process of removing water from a raw material having a high moisture content, which consists in continuously circulating previously dried material through a mixing space, an enclosed grinding space and a separating space, continuously circulating a stream of heated gases through the grinding space into the separating into the grinding space, introducing a measured flow of the raw material into the mimng space so as to obtain a mixture of predetermined moisture content, introducing the returned to the mixing space, concentrating the fine materialsremaining in suspension in the gases leaving the separating space in a gas stream to be returned to the grinding space and venting the remainder of these gases, and adding dry heated gases to the gas stream to replace the ases vented.

- WILLIAM B. SENSEMAN. 

